Supercooling points and the presence of antifreeze compounds were measured for both nymphs and adults of Steganacarus magnus (Nicolet) collected from a coniferous forest soil in southern England in March, June and November. The mean supercooling point of nymphs was −14.4°C and of adults, −11.7°C. Acclimation to low temperatures (1–2°C) did not alter these values significantly. The total concentration of antifreeze compounds in the nymphs was 4.46 μg mg-1 and in the adults 0.91 μg mg-1. These results are compared with similar data for other species of cryptostigmatic mites.